This is the engine management warning light and it comes on when a fault is detected by the engines computer which stores a fault code. Your garage will need to carry out a diagnostic check to determine what the fault code is.

Your daughter should be ok to continue to drive her car, unless it has a missfire, but I would recommend having the check done as soon as possible. If you do continue to drive, I would recommend that you try to keep the engine speed down and try to avoid prolonged motorway speeds. If you have a missfire, then the catalytic converter can become overheated, which will cause irreparable damage to the cat.

If the problem is safety critical, the engine will be placed into a limp mode, to prevent any possible damage from occurring, and you will feel a drop in performance.

Yeah, should be fine as long as she takes her time, as long as it isn't miss firing. Can you ask her if the engine is running smoothly, or feels like it is juddering when it is revved up? If it's running smoothly, then it should be ok.